Sinonasal aspergillosis is a frequent cause of nasal discharge that occurs in otherwise healthy, young to middle-aged dogs. A local immune dysfunction is suspected in affected animals, and the role of increased interleukin-10 mRNA expression in the nasal mucosa of affected dogs is currently under investigation. Despite recent advances in imaging techniques, the "gold standard" for diagnosing the disease is direct visualization of fungal plaques during endoscopy or observation of fungal elements on cytology or histopathologic examination. Treatment can be challenging; however, the use of topical enilconazole or clotrimazole through noninvasive techniques has increased the success of treatment and decreased the morbidity and duration of hospitalization.